1. Field of the Invention
The present invention relates to image forming apparatus such as a copying machine having various indication functions and various paper feed and transport functions.
2. Description of the Prior Art
Such type of copying machines are known in the art which can detect any trouble occuring in the machine and indicate it. Diagnosis instruction keys, a number of LEDs and others necessary for carrying out such detection and indication are disposed at the operation part of a copying machine as separate and particular members. Therefore, the objects whose trouble is to be detected are limited to a necessary minimum number. Furthermore, since a large number of LEDs and switches are arranged on the operation and display parts to watch troubles, the operation and display parts are made complicated and expensive.
Applicant of the present application has already proposed a copying machine in which the place where paper is jamming is indicated and running low of toner is notified making use of numeral indicators which are normally used to show the number of copies to be made and the number of copies already completed. This is the subject of Japanese Patent Application Laid-Open No. 66,432/1977.
However, the known copying machine is provided with no means for checking trouble of various sensors and detectors themselves provided for timing control and jam detection. It is not impossible to check trouble or error of such sensors and detectors themselves. But, the number of the objects to be checked is too large to do it. Detection circuits and indication circuits required therefor will become unduly large and complicated. Therefore, the number of objects must have been limited to a minimum. This, in turn, limits further improvement of reliability of the copying machine.
On the other hand, if checks and indications are made for all objects which one considers should be checked, the operator can hardly recognize what kind of trouble it is when any trouble is detected and indicated.
There is also known the type of copying machine in which keys are used to preset the number of copies to be made. These keys occupy a relatively large area of the operation part. If a number of input means for presetting a copy mode and for trouble diagnosis and various indicators are provided on the operation part in addition to numeral keys, then the operation part will become too much complicated to operate.
Recent developments of copying machines have made it possible to produce a large number of copies at high speed without interruption. In such a copying machine, sometimes two or more paper sheets are present in the paper path within the machine at the same time. Therefore, when even one of the sheets present in the path is jammed, all the sheets in the machine must be discarded including the copy sheet already completed. This is a loss of money and also against the purpose of speed-up in operation. Moreover, it is difficult in this case to locate the jam place and to know the number of sheets remaining in the machine. In the worst case, the copying machine restarts copying with any one of the jammed paper sheets remaining in the machine, which will bring forth a jam trouble again.
Generally, sheet storing, sheet supply, sheet feed and sheet discarge sections in the known automatic copying machine are so designed as to hold the same operation mode. There are known few machines in which the above mentioned sections can be controlled differently according to the various conditions of process sequences, troubles and the like. Therefore, the known copying machine necessitates the operator's time-consuming and troublesome work.